User authentication is required in order to provide secure user access to a telephony service. However, current user authentication processes can be frustrating for the user; for example, a user requesting a service over the telephone may be required to respond to numerous requests for passcodes or personal data. These requests may be repeated when a user is passed to another operator during a call. The user may find passcodes difficult to remember, yet these passcodes are easy to intercept. Moreover, personal data for the user may be easily obtainable from various public sources.